<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>index</title>

    <style>
        *{
            margin: 0;
            padding: 0;
        }

        .container {
            width: 960px;
            height: auto;
            overflow: hidden;
            margin: 20px auto;
        }

        #num-input {
            width: 300px;
            height: 30px;
            border: 1px solid #000;
            background-color: ghostwhite;
            border-radius: 2px;
        }

        button {
            width: 60px;
            height: 30px;
            background-color: ghostwhite;
            border: 1px solid #000;
            border-radius: 2px;
            margin-left: 20px;
            cursor: pointer;
        }

        #display {
            width: 100%;
            height: auto;
            overflow: hidden;
            border: 1px solid #000;
            margin-top: 20px;
        }

        .num {
            width: 40px;
            height: 40px;
            color: #ffffff;
            background-color: red;
            float: left;
            margin : 10px;
            text-align: center;
            line-height: 30px;
            cursor: pointer;
        }
    </style>
</head>
<body>

<div class="container">
    <input type="text" id="num-input">
    <button id="left-in">left-in</button>
    <button id="left-out">left-out</button>
    <button id="right-in">right-in</button>
    <button id="right-out">right-out</button>

    <div id="display"></div>
</div>

<script src="task.js"></script>
</body>
</html>